1. Field of the Invention
This invention relates generally to the monitoring of transmission lines, and more particularly, to the detection and measuring of foreign voltages on communication lines such as telephone subscriber lines.
2. Description of the Related Art
Communication lines, such as subscriber lines in a telephone network, are susceptible to being affected by foreign voltages. Foreign voltages are faults on the subscriber line that are more positive than ground, or more negative than the battery voltage of the telephone network. These faults can adversely affect the operation of the telephone network or can cause damage to connected equipment.
Subscriber lines are tested to detect, among other things, foreign voltages. These tests may be performed as a part of normal maintenance or in response to a customer complaint or service outage. Typically, these measurements are conducted manually or through the use of test equipment external to the subscriber line circuitry. The use of external test equipment is costly, based on the expense of the test equipment and also the time required to connect the equipment to a particular subscriber line being tested.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
In one aspect of the present invention, a sensor capable of being coupled to a transmission line and monitoring a foreign voltage on the transmission line is provided. The sensor includes a voltage monitoring circuit. The voltage monitoring circuit is adapted to operate in a foreign voltage detection mode in response to receiving a first logic signal and a foreign voltage measurement mode in response to receiving a second logic signal.
In another aspect of the present invention, a method for operating a circuit to detect and measure a foreign voltage on a transmission line is provided. The method includes providing a first logic signal to configure the circuit to detect a foreign voltage. The foreign voltage is detected on the transmission line in the circuit. A second logic signal is provided to configure the circuit to measure the foreign voltage, and the foreign voltage is measured.